At the request of IAEA, colleagues at the University of Toulouse are conducting very high resolution model simulations of the Fukushima radiation release into the ocean. This is an excellent approach to help answer the questions raised by the controlled and uncontrolled radiation releases into the ocean at the Fukushima site. The model achieves high resolution in the coastal zone of Japan and provides high fidelity around a specific period of time.
The SIROCCO model (SYMPHONIE) resolution is 600 m at the coast and is 5 km offshore. The model is nonhydrostatic, making it particularly well-suited for shallow regions. The atmospheric forcing is from the ECMWF high quality global 25 km resolution weather model. The SIROCCO model shows frequent southward currents (left panel above shows a snapshot). And also an anticyclonic (clockwise) eddy nestled south of Fukushima and adjacent to the fast Kuroshio current. These two features (the occurrence of southward currents near Fukushima and the eddy to the south) were also found in the Naval Research Laboratory’s global HYCOM simulations shown in a prior post. But the SIROCCO model also shows intensifications of a local northeastward current (right panel above shows a snapshot) that may be caused by more frequent northward and northeastward winds over the past week (see recent airborne plume forecast posts). The coastal ocean is highly variable and very responsive to the winds.
The SIROCCO model has a tracer release capability (a snapshot from April 4 is shown above). And in the simulations, the timing of the recent radiation releases into the ocean (controlled and uncontrolled) have tended to transport the material in the local northeastward current. This snapshot is from a dissolved tracer simulation, and they did scenarios with a particulate tracer and also airborne deposition on the ocean. This represents a highly valuable set of simulations.
In good news from the Fukushima site, the identified uncontrolled release into the ocean at reactor 2 has been contained today. The controlled release of low-level radioactive water continues.